Currently, oscillators are used in various circuits within a feedback loop or a control loop. Such circuits may include phase locked loop circuits, filters, modulators and/or the like. Such circuits may be used for various applications that may include frequency synthesis and clock generation/recovery that may require a local time base (or an output clock). The local time base may be associated with particular properties that are required to be controlled within a specified limit. Example properties may include frequency stability, jitter, and/or phase noise. Phase noise or jitter may correspond to a measure of the fluctuations and variations in the local time base transitions with respect to time. Phase noise is usually represented in frequency domain.
Further, generation of the local time base may require an external timing reference. In certain scenarios, when oscillators are used for frequency synthesis application, a crystal resonator may be used as the external timing reference for generation of the local time base. Desirable local time base properties in the frequency synthesis application are low frequency variation (high stability) and low phase noise. Further, in certain scenarios, when oscillators are used for clock generation/recovery application, an incoming data stream, complete with signal impairments, such as jitter, may be used as the external timing reference for generation of the local time base. A desirable property of the local time base in the clock generation/recovery application is the ability to accurately track the variations in phase noise and/or jitter of the incoming data stream over a wide band of frequencies. The amount of phase noise or jitter suppression or the accuracy to track the phase noise or jitter may be dependent on a bandwidth of the closed or feedback loop circuits.
Various methods have been utilized in the past to achieve phase locking of the local time base to the external reference in the clock generation/recovery applications. For instance, a conventional phase locked loop (PLL) circuit that may include a phase detector, a loop filter, a voltage controlled oscillator (VCO), and an optional frequency divider may be used to achieve the local time base locked to an external reference. The bandwidth of the closed loop PLL circuit may be determined by the gain of the VCO, the characteristics of the loop filter, and the latency around the loop. The latency around the closed loop of the PLL circuit may be determined from the phase detector input to the VCO output. Such PLL circuit have a very high latency that reduces or sets a limit to the maximum feasible or realizable bandwidth. Therefore, there is a need of an advanced injection-locked oscillator that may have a low latency and high bandwidth that results in high accuracy over a wider band of frequencies to track the phase noise or jitter of the incoming data stream in clock generation/recovery applications. Further, enhanced minimization of the phase noise or jitter in frequency synthesis applications, may also be desirable.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of described systems with some aspects of the present disclosure, as set forth in the remainder of the present application and with reference to the drawings.